Optical gap and fundamental gap of oligoynes and carbyne

Abstract

The optoelectronic properties of various carbon allotropes and nanomaterials have been well established, while the purely sp-hybridized carbyne remains synthetically inaccessible. Its properties have therefore frequently been extrapolated from those of defined oligomers. Most analyses have, however, focused on the main optical transitions in UV-Vis spectroscopy, neglecting the frequently observed weaker optical bands at significantly lower energies. Here, we report a systematic photophysical analysis as well as computations on two homologous series of oligoynes that allow us to elucidate the nature of these weaker transitions and the intrinsic photophysical properties of oligoynes. Based on these results, we reassess the estimates for both the optical and fundamental gap of carbyne to below 1.6 eV, significantly lower than previously suggested by experimental studies of oligoynes.

A review of functional linear carbon chains (oligoynes, polyynes, cumulenes) and their applications as molecular wires in molecular electronics and optoelectronics

“…60 A recent combined experimental and computational study has reassessed the estimates for both the optical and fundamental gap of carbyne to below 1.6 eV, which is significantly lower than previously suggested values. 68 An interesting feature of single-crystal X-ray crystallographic studies of oligoynes with various end-groups is that the backbones often have a nonlinear curved geometry. 69,70 It is noteworthy that the selection of oligoynes shown in Fig.…”

Stability of the polyynic form of C18, C22, C26, and C30nanorings: a challenge tackled by range-separated double-hybrid density functionals

“…Carbon-based compounds exclusively made from sp-hybridized C atoms may exist in different forms: from linear chains to cyclic nanorings to polycyclic cages, [1][2][3][4] all of them gathered under the notation C n (and also dubbed as cyclo[n]carbon) with n indicating the number of C atoms. However, these systems despite their apparent simplicity represent a challenge from both synthetical and theoretical points of view.…”

Cyclic vs. acyclic alkyne towards Hg2+ ion detection: combined experimental and theoretical studies

“…[8][9][10][11][12][13][14] There are numerous studies on isolated terminal alkynes, internally conjugated 1,3-dialkyne systems and oligoynes, both in cyclic and acyclic systems, which account for their stability and respective areas of applications. [15][16][17][18][19] For example, conjugated alkyne systems in long-chain or cyclic form have been used in various applications, ranging from natural products to optoelectronics, which is dependent on their unique molecular structure. 15,16,20 However, a clear comparative picture of cyclic and acyclic structures having alkyne functionality as a point of interest is rather rare.…”